New Roles for the Submarine

Deep-diving, quiet-running descendents [sic] of World War II wolfpack and midget submarines, armed with sensors and weapons and power plants of the 1970s need not be nuclear to take on a new menace, and provide a new strength for U. S. seapower.

Excluding the negative and increasingly narrow power of its nuclear weapons—a dismal capability of last resort for the infliction of “unacceptable damage” when one’s own country is already in extremis—a modern navy has had three basic missions. These have been, first, to keep the oceans free for the movement of its merchant ships (which, to all but the iconoclasts, means surface ships); secondly, to project its military power across the seas to foreign shores, again in hulls that float on or skim over the ocean surface; and, finally, to “show the flag,” that is, to impress an increasingly skeptical world with the alleged power of its massive hulls. Since the most elementary prudence requires the maintenance of at least the first two of these capabilities, the question—in an era of continual and even revolutionary technical change—is “How?”

To quote a foreign, rather than an American opinion which is gaining increasing acceptance, “The financial and technical effort devoted to ASW by both East and West is very great and seems to be increasing. The range of ASW techniques is very wide. Nevertheless, all the evidence suggests that the balance of advantage continues to lie with the hunted submarine.”[1]

The belief is now stronger than ever that, certainly in favorable areas, and perhaps in far greater ocean regions, properly handled submarine blockades combined with (as circumstances permit) other forms of harassment, can destroy or drive into port present naval and merchant fleets.

Rear Admiral Edward Wegener, Federal Germany Navy (Retired), in examining Mahan’s teaching in light of modern technology remarks, in a frame of reference that does not include many potential improvements, “The submarine has become so powerful an instrument of naval warfare, as to have entered into competition for mastery of the sea. The nuclear-powered submarine in particular is a weapon that is just as much a danger to warships—surface and subsurface—as against cargo ships.”[2]

If that is so, conventional approaches to carrying and protecting ocean commerce in time of war, and the conduct of naval operations, are no longer valid. Nor is salvation likely to be found in more exotic approaches such as air-cushion vehicles, large cargo aircraft, or the like. These are most likely to be useful as auxiliary devices efficient only in favorable situations, and vulnerable to a host of weapons.

It may be well to remember that, twice in this century, when the submarine was, on balance, far less technically favored over its enemies than now appear to be the case, it took an ASW effort some ten times more massive than the U-boat campaign to save England from strangulation—and by a hairs-breadth. As for the Imperial Japanese Navy and merchant marine which could not mount so massive and effective an ASW effort, a relatively small fleet of American submarines crippled for over a year by ineffective torpedoes, was a chief cause of their destruction.

One can easily foresee a situation when no practical level of ASW will be able to break a blockade based upon submarines.

On the face of it, this possibility—indeed probability—involves a degree of disaster so great that theft is a strong temptation, whose sources any psychiatrist can describe, to brush the entire thesis aside as hare-brained. Arguments about the proper basis for our naval power become academic if we lose our ability to move bulk cargo by sea.

Although the final answer to a submarine blockade is likely to involve the use of a wide variety of other submarines, including cargo carriers, there is no intention here to denigrate efforts to improve conventional ASW or to increase the resistance of any form of surface ship to submarine attrition. Nor is it forgotten that technological superiority cannot overcome ineptness timidity, or completely wipe out the advantages of geography. But, as the United States should certainly know by now, this country has no monopoly on intelligence, competence, or iron determination. And today’s submarines, let alone those of the future, are not as much the victims of geography as are surface ships.

The factors that are giving submarine fleets the power to control most ocean areas are numerous, and not all of them are overtly spectacular. Let us review some of the more important:

► There has been a slow, steady improvement in life support systems which owes much to the space effort. It is relatively simple business today to make a submerged submarine livable for months. In World War II, a submerged submarine was in trouble with its air supply in less than 24 hours.

► The earth has been covered with layers of sensors and communicating systems. The motivation for many of these sensors has been primarily to fight the submarine. On balance, however, it may very well be that the submarine will profit the most from these sensor-cable radio links. A sensor—for example, an ocean surveillance satellite—which can detect a submarine, can detect a surface vessel far easier. Any nation with a coastline, or with allies who abut on salt water, can install its own seabed sensors and do what it wishes with the resultant data.

In the past, a deeply submerged submarine was cut off from the world. Today, a number of methods are available by which it can send and receive data at rates which are ridiculously low when compared to the capacity of radio links or laser beams in air or space. But the difference between a submerged submarine completely cut off from her bases and friends, and one capable of receiving or sending at, say, half a bit per second, is a difference in kind, not in degree. Of course, if the submarine is willing to stick an antenna above the surface, she is as thoroughly tied into these planetary and satellite communication systems as any other craft.

► There has been an enormous improvement in the accuracy, reliability, and availability of inertial navigation. This is of no great importance to the surface ship, which has navigated quite adequately by the stars for centuries, and now has all sorts of radio navigation aids. But inertial navigation is vital to the submarine. It is growing more accurate and, above all, cheaper by the month.

► There is, among the world’s submarine designers, a preoccupation with the reduction of radiated and self noise, and in fact, with the reduction of all of the submarine’s signatures. In this regard, it is more significant to quote the foreign literature than our own. Russian comments on American submarine design trends are studded with references to changes that affect noise output. If there is one pitfall above all others that ASW should avoid, it is the fallacy that the enemy will be using noisy submarines. Noisy snorkelers and noisy nuclears have been built in the past, and some still survive. Even the quietest of submarines may be noisy at high speed. But ultra-quiet submarines can be built. These will be the enemy which must be defeated if there is to be such a thing as conventional ASW.

► The variety and capability of submarine-launched air-flight weapons continues to increase. The impact of homing weapons on submarine warfare can be both direct and indirect. It may well be, for example, that the contest between the manned plane and the homing missile is not necessarily separable from the future of ASW. A change in technology, be it missile, laser, or what have you, that reduces the field of action of the manned plane, will drive another nail into ASW’s coffin.

To return to the antiship missile: Such weapon systems, minus the significant capability of underwater launch, are now being built by the United States, the Soviet Union, Great Britain, France, Italy, Norway, and Israel. To read the advertisements in magazines concerned with military matters, all one seems to need is money in order to obtain a missile system of this kind. Underwater-launched tactical missiles also exist, and are sure to grow in number. It is this latter development with its long stand-off range, which, in some eyes, has broken the back of conventional ASW, at least for the time being. The historical truth that defenses eventually evolve to meet new weapons does not specify a time.

► Even more significant innovations lie in the realm of propulsion. It is a near-certainty that propulsion techniques encouraged by space technology will become practical and economical in submarines. The system of greatest interest is the fuel cell. It is possible, however, that radioisotope generators in larger sizes than are now available (which is about 10 kw.), or relatively small reactors with direct conversion to electric power, will be practical drives for submarines.

Fuel cells need not necessarily depend upon liquid hydrogen and liquid oxygen. A wide variety of other oxidizers and fuels, many of them liquids at ocean temperatures, are feasible. For example, hydrocarbons and air are being used in fuel cells now powering apartment houses—a development of considerable interest to the public utilities. Hydrogen peroxide and hydrazine are low-cost chemicals which have been mass-produced for years. For that matter, liquid hydrogen can cost as little as eight cents a pound in bulk. The space activities of several nations have indicated that, with proper precautions, such fuels can be handled just as safely as U-235 or plutonium. The net effect will be to make possible fast submarines with underwater endurance measured in weeks and in sizes under 1,000 tons. In sight here is an improvement of perhaps hundreds of times in what is referred to as the full-speed period of a battery submarine. It also remains to be seen whether diesel-electric or gas turbine-electric submarines, if built with all of the sophistication now feasible with respect to noise output can be cavalierly disregarded by ASW. The preoccupation of the United States Navy with submarine propulsion systems of an endurance many times that of a crew should not blind ASW to the dangers of submarines with less ultimate power plants.

These various specifics lead to the same conclusion—the technology of the next decade will have the capability to produce submarines far more versatile, less costly, and more effective than the nuclear attack craft now in existence.

Admiral Alfred Thayer Mahan’s axiom that technology changes tactics, but not strategy, still remains true. In spite of the trends just mentioned, and no matter what happens to the balance of power between submarines and surface ships, control of the sea is basic to world influence. This holds even for the self-sufficient powers, of which there are now only two—Russia and China. The United States might continue to exist if it lost control of large ocean regions, but not as a world power. As for Japan and Western Europe, control of the sea lanes, over which they receive food and raw materials, is absolutely vital to their existence.

In view of the efforts which the United States has launched in order to alleviate its balance of payments problems and its internal economic ailments, the day when Europe and Japan must provide for their own defense may be much closer than official statements imply. It therefore takes little predictive capability to deduce that the design of new, cheaper, and improved submarines will become, if it is not already, a major international concern.

The near-certainty that nuclear weapons will be available to an increased number of maritime nations will make conventional submarine blockade more likely rather than less. Many methods for reducing the cost of fissionable material are under development. For example, it has been predicted that, by 1980, power reactors around the world will be providing plutonium at the rate of 100 kilograms per day.

General availability of nuclear weapons will remove the threat of nuclear war as the final deterrent to an assault on ocean commerce, particularly in limited parts of the world and for clearly limited aims. As Vice Admiral Hyman Rickover stated in September 1971, with respect to the U.S.S.R., “If they now succeed in building a Navy which can prevent our Navy from supporting overseas military operations, then they can have their way over any issue for which we are not willing to risk nuclear war.”

In a few more years, and surely before the end of this decade, not only the U.S.S.R., but also China, if not Japan, Germany, and several other countries, will have the power to inflict unacceptable damage on an enemy by nuclear means. If a nuclear power has the ability to wage conventional submarine warfare in an area or in a manner that does not put our survival at stake, how will we reply?

The nuclear attack submarines being built by the United States, Russia, and to a much smaller extent by Great Britain and France, suffer, as the French put it, from the defects of their virtues. They have extraordinary speed and endurance underwater and, to utter a heresy, perhaps much more than an attack submarine needs. Their large size has made them creatures of the deep seas. Yet, there remain other vast areas—the North Sea, the Sea of Japan, the Yellow Sea, the South China Sea, and all the continental shelves of the world—which are of the utmost importance to ocean commerce and to naval power. We cannot, we should not, turn our backs on these areas and say we will not operate submarines there. If America does not attempt to control these ocean areas by the design of appropriate equipment, others will. God did not grant the United States an irrevocable claim to control of the sea. It does us no harm to remember, for example, that, after Pearl Harbor, most of the Pacific was barred to American surface ships and planes for over a year. Only our submarines—armed with torpedoes that functioned erratically—could penetrate this enormous area.

The potentialities are immense for new forms of submarines, some of them very large, yet many of them so small and quiet that they would be difficult to find by current types of sensors.

This country’s great capability in nuclear propulsion should not be a barrier to experimentation with the propulsive techniques that will make these small—something less than 1,000 tons—submarines practical.

Moreover, a sharp reduction of the size of crews would result in a reduction in morale and administrative problems and perhaps a return to the wholesome condition in which there is an abundance of volunteers for this service.

The most striking advantage of these smaller, more silent submarines, however, would be their extraordinarily low noise levels. Such submarines would be exceedingly difficult to locate and track by passive sonar. If they are given sufficient depth capability to literally hug the bottom, they will be difficult to find by active sonars. And if they are built of titanium, fiberglass, plastics, or stainless steel, they won’t have a magnetic signature worth mentioning.

Of the many reasons that they will not likely be stopped by active sonar, let us consider a submarine capable of operating at 4,000 feet—some submarines can attain 10,000 feet—and equipped with wheels. A few submarines have carried wheels. Now let us see how our wheeled submarine might proceed from Murmansk to New York, or vice versa. A look at the depth contours of the North Atlantic reveals that, except for one stretch of about 500 miles in crossing the Labrador Basin, the submarine could use its wheels. Let us hasten to add, that we are not advocating the use of wheels on submarines. We wish merely to make the point that, over enormous regions of the oceans, a submarine of substantial depth capability could “fly on the deck,” and be exceedingly difficult to detect by active as well as passive sonar.

These small submarines must be conceded a dash speed as great as their larger nuclear cousins. Relevant here is a statistic which is one of the facts of life of naval operations. Many years ago the British declared that their destroyers used more than 20% of their engine power only 4% of the time, which is why the British, the Germans, and now the Americans are going to base-peak power plants in surface ships. Skippers of nuclear submarines reveal that their average speed is quite low, not markedly different from the average speeds of diesel-electric boats.

What seems to be obvious, then, is this: if small submarines can generally conserve their energy and retain it for short bursts of speed, they will be able to make an approach on virtually any ship they detect—surface or submarine. In fact, although it is hard to see much promise, or at least cost-effectiveness, in ASW contests between 5,000-ton attack submarines, the idea of pitting very quiet, small submarines against larger and inevitably noisier submarines is, to say the least, intriguing. The larger submarines will be noisier because, given the same state of the art in silencing, it is easier to quiet a 2,000-h.p. system than a 20,000-h.p. system.

If ASW environments become so hostile that it is necessary for submarines to have truly deep submergence capabilities, it is easier and cheaper to build a small hull capable of reaching a given depth than to build a large one. Alvin, the Woods Hole research submarine, will soon have a titanium hull and, with it, a sharp increase in depth capability (from approximately 6,000 to 10,000 feet). The idea of building a 688-type submarine out of titanium is, at least today, unthinkable. In 1968, for example, a Russian writer reckoned that titanium was about 11 times more expensive than HY-80.

The relative prices of metals, however, are not static. One of the French kings who followed Napoleon had a set of tableware made of aluminum because it was such a rare and costly metal. Time, technology, and mass production will reduce the price of titanium, fuel cells, radioisotope generators, inertial platforms, and a whole host of materials and devices that are now barred to submarines.

One new function for small, deep-running submarines will be as elements in a war of sensors. U. S. planes in Vietnam, and Israeli planes in the Sinai, have struck repeatedly at radar installations. There will inevitably be an underwater parallel. One notes with a mild degree of astonishment that, as of 1969, there had been more than 30 ocean-bottom-habitat experiments. Most designers say that the optimum ocean habitat is mobile—a submarine with lock-in, lock-out capability. Divers have already worked in the open sea to depths of 850 feet, a greater depth than was available to almost any submarine of World War II. The potential for sabotage and guerrilla activity in such developments is a quantum jump above anything that ocean warfare has seen in the past.

Of more importance, however, than any specific mission now within the capabilities of the proper combinations of new submarine and diving technologies, is the overall ability of small submarines to operate in waters too shallow or too restricted for larger vessels.

The May 1971 issue of the Naval Review carried two articles that bear on this point. One, by a major general in the Royal Marines, dismissed the North Sea as an unsuitable arena for submarines. “Lack of depth,” the author said, “increased the vulnerability of submarines—visual, infra-red, magnetic anomaly, and others as well as sonar—while mining would be likely to restrict their area of action.” That is very true if we are thinking of 5,000 or 7,000-ton submarines.

But, in World War II, submarines operated successfully in even more restricted waters. One was the U-47, which entered Scapa Flow, sank the Royal Oak, and escaped. She was a Type VII-B U-boat, displacing 753 tons on the surface, 857 tons submerged. Submarines no bigger, and sometimes smaller, than the U-47 have repeatedly shown that they can operate in the deep seas and can successfully complete two- and three-month patrols. Even the X-craft and still smaller midget submarines which, on balance, performed ineffectively in the past, take on a new menace when supplied with modern life support systems, navigation gear, and propulsion plants with orders of magnitude more endurance than that of the World War II midgets.

In that same issue of the Naval Review, Commander Hideo Sekino, of the Imperial Japanese Navy (Retired), discussed Japan’s immense problems in ASW. He pointed out that 40% of Japan’s internal transport moves by sea; thus, stopping the shipping in Japan’s Inland Sea alone would cripple Japan’s economy. As for the Sea of Japan which, although roughly the same dimensions as the North Sea, is much deeper, he agreed that it was generally fit for submarine operations but excepted the five narrow straits that lead into it, and implied that sonar conditions were excellent for the use of fixed detection facilities.

An attitude that shallow and confined waters are no place for submarine operations is equivalent to saying that the infantry should move only on good roads in well-protected convoys and consider difficult terrain as off-limits. The attack submarine has always been a maritime guerrilla. Even if it becomes, as many now think possible, an overwhelming threat to major surface naval vessels, it will remain most deadly when operating where it is least expected.

If undersea power attains the potential that has been implied here, and the key to maritime supremacy becomes the submarine, a period could emerge when the only long-haul carriers that exist are submarines, when the only surface vessels that can survive are high-speed, short-legged coastal types, and when aircraft are essentially out of touch with the action because—except when a submarine is crippled or is momentarily at high speed—both passive and active sonobuoys have pathetically short ranges.

As the world’s per capita appetite for oil and other raw materials has increased, and as the world’s population has grown, merchant fleets have increased in unit as well as in total tonnage. Relationships between the world’s major maritime powers have changed. Further upheavals are likely before this century is out. It would take a most extraordinary prophet to postulate today the primary targets of U. S. submarines in the year 2000, or where they will lie.

There are already more than 200 superships—ships with loaded displacements of 200,000 tons or more—afloat. Of the approximately 83,000 merchantmen that have been predicted for the end of this century, some 2,000 will be superships. Such ships cannot be hidden, and quite likely, cannot be protected. Given the tensions of this world, and what passes as international morality, it takes a remarkable optimist to believe that no nation will ever be tempted to destroy some of these exceedingly vulnerable craft.^[3] These new merchant ships have been allowed to assume their forms unchecked by military considerations—their design evolving under purely economic forces—because of the quarter-century of peace at sea maintained by a U. S. Navy whose capabilities in controlling the sea are increasingly questioned.

The main point which arises from the changes of the past quarter-century is that relationship which once existed between naval vessels and planes on the one hand and submarines on the other, are at best uncertain. They may very well have been distorted to the point where they are unrecognizable, that is, if put to the test, they will yield results utterly at variance with our expectations.

Yet, we cannot give up control of the seas; we cannot renounce our right to carry goods wherever and whenever we wish. Therefore, a number of necessary realignments in planning—some quite painful—must be evaluated. Efforts to build small submarines with nonnuclear, or at least, nonreactor propulsion systems must be stepped up. Cargo submarines must be built and tested. It should be noted, however, that cargo submarines at the 170,000-ton or 250,000-ton displacement level, such as those proposed for Arctic oil routes, are too specialized to break the usual blockade. The Navy can—indeed, it must—use submarine cargo carriers of much smaller tonnage and draft. The point previously mentioned—that the noise output and, thus, the detectability of a ship is greatly affected by its size and horsepower—holds true for cargo submarines as well as military. The great cost-effectiveness of large, unmolested surface ships is not denied. But, if the movement of such ships can be stopped, their effectiveness in a militarily benign climate is immaterial.

Air-cushion vehicles and hydrofoils, with little or no hull in the water, are not necessarily satisfactory alternatives. They are good radar and acoustic targets. Nor are they invulnerable to air flight missiles. And, of course, they are prodigious consumers of fuel.

The keys to ocean power are changing, and however unpleasant the consequences, these must be determined and faced. Since the future cannot be defined with precision, it is necessary to describe it with families of contingencies, to which families of solutions must be found.

Surely these solutions will include new forms of submarines, both larger and smaller than those the Navy now deals with, new power plants, new weapons, and a far wider gamut of missions. Above all, the Navy must address the problem of ocean transport in terms of blockade, for in the absence of some extraordinary improvement in the efficiency of aircraft, no other service or organization can.

Let us describe a scenario that can be devised to support this recommendation. A submarine blockade has been placed around one of our island bases, the intent being to cripple it as a base for our offensive operations, rather than to destroy it. It has been made clear to us that we face no threat from nuclear weapons or even conventional attacks on the islands. Let it be conceded that, as long as fuel is available, ASW surface ships and aircraft can conduct an intensive surveillance of narrow areas around the main ports so that, if a ship has survived the gauntlet further out, she can enter port and unload on the surface.

But on the long routes to this isolated archipelago, merchant ships and even task forces have been taking unacceptable losses. Petroleum reserves are running down, and so is the mobility of the ships and planes based upon the islands.

It can’t happen? What can prevent it?

__________

Paul Cohen is president of Subcom, Inc., and has been concerned with research, development, and design of submarine launching, weapon and fire control equipment since World War II. Prior to the formation of his own firm in 1966, he was Research Department Head for Undersea Warfare at the Sperry Gyroscope Company. He is a member and was for several years chairman of the Detection and Control Section of the Underwater Ordnance Division of the AOA, and is currently a member of the NSIA Ad Hoc Study Group on Acoustic Communications. He is the author of the The Realm of the Submarine, Macmillan, 1969.